additives feature | PVC stabilizers
to be made. An example is Reagens’ recently developed octyltin stabilizer, Ratinor 894, which has a very low content of DOTE (2-ethylhexyl 10-ethyl-4,4- dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetrade- canoate). “The recent inclusion of DOTE in the
candidate list of Substances of Very High Concern (SVHC), might generate concern about the use of octyltin stabilizers,” says the company. Ratinor 894 enables production of PVC compounds and articles containing less than 0.1 % of DOTE, removing the need
Consumption of PVC stabilizers in the EU by type in 2014 Source: ESPA
manufacturers and downstream users has been critical in this process. PVC stabilizers are present in PVC com- pounds at a low percentage only but they are crucial ingre- dients to produce articles and maintain their properties throughout their entire life cycle. ESPA members are continuously adapting stabilizers to address the new regulatory constraints, including REACH.” Asked whether any completely new stabilizers are
likely to appear on the market, Cavallero replies: “I am not aware of any, but I would not exclude the possibility. In recent years, additive suppliers have been making steady progress in developing stabilizing systems, but I do not expect any breakthroughs.”
New octyl tin stabilizers While there are no completely new types of stabilizers on the horizon, improvements to current types continue
for users to notify customers of the presence of an SVHC.
“This high mono-octyl tin shows an excellent early
colour, and just a slightly weaker long-term heat stability because of its intrinsic lower tin content,” says Mario Berna, R&D and technical service manager at Reagens. “But thanks to Reagens’ well established co-stabilizers such as Reapak B-NT/7222, which is the only non-toxic compound showing a dramatic thermal synergy with organotin stabilizers, the combination of the two keeps the cost/performance at the lowest possible level without using any SVHC substances.” Berna adds that this is true even for articles where the use of octyl tins are relatively high, such as extruded sheets.
Berna says that Reagens has also developed a new
range of octyl tin stabilizers – Reatinor 830 Z Gamma – with extremely low DOTE content for very demanding
Assessing the alternatives to lead
The European Stabiliser Producers Association (ESPA) has put together this useful summary of the main alternatives to lead-based stabilizers for various PVC formulations and applications. Calcium-based stabilizers: These are the main alternative to lead-based PVC stabilizers. In Europe, they are now largely used in wires and cables, window and technical profiles, and pipes and fittings. It is possible to switch from lead to calcium-based stabilization without making changes to processing machinery such as extrusion screws and tools. Calcium-based stabilizers are available in different physical forms such as powder, granules, pastilles or flakes. Calcium- based stabilizers are also used in rigid PVC calendering film production when improved organoleptics characteristics are required, for instance as alternative
20 COMPOUNDING WORLD | June 2015
to tin mercaptides in transparent food packaging application or as alternative to tin carboxylates in heat-shrinkable blown films and candy wrap. Liquid mixed metal stabilizer
systems: These are based on carboxy- lates of barium zinc, calcium, magnesium or potassium. Applications include: calendered films; extruded profiles and hoses; injection moulded footwear; and plastisols for flooring, wall coverings, artificial leather, coated fabrics, or toys. Liquid mixed metals such as BaZn, CaZn and MgZn generally require the addition of co-stabilizers, antioxidants and organo-phosphites to provide optimum performance. Solvents such as hydrocar- bon solvents and plasticizers are used to adjust the formulation’s viscosity. BaZn stabilizers have replaced cadmium-based stabilizers in many PVC semi-rigid and
flexible applications. Tin stabilizers: In North America, tin
systems are used for almost all-rigid PVC applications, while in Europe they are mostly used for rigid, transparent applications where rigorous processing conditions require particularly good stabilization. Tin stabilizers maintain high transparency, and reduce the tendency of parts to yellow. They are also suitable for use in opaque applications, particularly where light colours are required or when process requirements are demanding (thick plate extrusion, furniture films). Tin stabilizers provide very good processabil- ity, enabling high throughput and no plate-out. They are approved for use in food-contact and potable water applica- tions. Some types are approved for use in rigid medical applications. ❙
www.stabilisers.eu
www.compoundingworld.com
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